FI12328U1 - Rotating drum screen - Google Patents

Description

ROTATING DRUM SCREEN

The invention relates to a rotary drum screen for pulping pulp having an axis of rotation inclined up to 30 ° to the horizontal, fed from the first end face with water mixed with a pulp which is thoroughly mixed within the drum screen by lifting and / or transferring elements. Such apparatus, for example described in DE 10 2012 219 708 A1, is most often intended to mix with water, grind and sort dirty recycled paper. For this purpose, water-mixed recycled paper is generally comminuted in the disintegration zone of the horizontal cylinder / drum screen by raising, scrolling and dropping, i.e., relative movements of the mass members relative to one another. In the associated sorting zone, the dissolved pulp is then to be separated from the debris. As the fine fraction passes through the perforation or sorting apertures, the coarse fraction containing the debris is separated and led away from the drum screen. The process for treating recycled paper using such or similar drum screens has the advantage of particularly gentle disintegration, which applies to both sensitive fiber species and unwanted foreign matter to be sorted. In this context, there has been a trend towards ever greater drum screens and increasing reject volumes. As a result of the rotation, more spinning and even braids consisting of cords, threads, gauze, etc. are formed in the center of the drum screen. These spinning loads burden reject removal and can even lead to clogging of the drum screen.

It is therefore an object of the invention to effectively prevent the formation of spinning at the lowest possible cost.

According to the invention the objective is achieved in that the sieve drum mounted inside of the vortex flow elements, the height of which is across the inside in the radial direction with respect to the axis of rotation of at least 25%, preferably at least 30% and especially at least 35% of the diameter of the drum screen. With these vortex flow elements, the pulp slurry is subjected to an intense vortex, which prevents or even prevents the formation and accumulation of spinning or reject plaits.

The vortex flow elements should extend as far as possible into the center of the drum screen. For this reason, it is preferred that the cross-flow vortex elements, the height of the inside of the sieve drum is at least 50%, preferably at least 75% and especially at least 100% of the average height of the sieve drum, which is filled with a mass of fibers in that section.

Generally, 20-40% of the inner volume of the drum screen is filled with fiber pulp slurry.

The vortex flow elements are particularly effective when they extend up to or even beyond the slurry surface. However, the requirements for the stability of eddy flow elements will increase with this. However, when the diameter of the drum screen is 4.5 m, however, the filling height may be at least 1.5 m. For this reason, it is advantageous for the vortex flow elements to be formed in sheets. These plate-shaped vortex flow elements should extend at least one specific directional component circumferentially and / or radially. The radial section of the disc gauge may be limited to cross the interior of the drum screen prevailing in height, while the circumferential alignment to minimize the flow resistance.

In order to prevent the formation of spin on the vortex flow elements themselves, they should taper towards the axis of rotation.

In order not to diminish the power of the lifting and transferring elements, the vortex flow elements should always be arranged between two lifting and / or transferring elements arranged in a row circumferentially. This also facilitates a secure attachment to the inner side of the drum screen.

To improve fiber handling, the disintegration zone following the first end page of the drum screen should be axially associated with a sorting zone in which the drum screen is perforated, whereby the fine fraction flows through the perforation and the coarse fraction is separated therefrom.

Because spinning can occur in both zones, the vortex flow elements should be arranged in both the disintegration and sorting zones.

The transfer ribs attached to the inside of the drum screen can be used as transfer elements due to their simple yet durable construction.

Alternatively or additionally, the transfer elements may also be formed, for example, into coils attached to the inner wall of the drum screen.

Accordingly, in order to achieve a sufficiently high transfer power, the transfer bars are inclined with respect to the axis of rotation. This means that the end of the transfer strip pointing in the direction of transfer follows in the direction of rotation.

siirtorimojen across the height of the screen drum inside face of the required transmission power can be varied.

In addition, the drum screen may also have one or more partitions which are open in the center and extend perpendicular to the axis of rotation. These partitions form an annular barrier over which the pulp and water are transferred from the inlet to the opposite end of the drum screen by means of transfer elements.

At the same time, the transfer ribs may be attached to the end of the drum screen and / or to the adjacent partition.

In order to promote the disintegration of the pulp and its mixing with water, there should be lifting lugs, without axial transfer power, arranged at least outside the area comprising the transfer elements, inside the drum screen. These crane arms preferably have a greater circumferential number than the crane arms. In addition, due to their misalignment, the crane slats have a lower height than the slant slats.

If several lifting arms are then axially arranged along the drum screen, then they should be at least slightly overlapping relative to one another in the circumferential direction of the drum screen to minimize vibrations.

In addition, a collection container should be provided below the drum screen for receiving the fine fraction and the runoff water.

The axis of rotation of the drum screen may be horizontal or inclined relative to the horizontal. With the incline toward one end downward, the transfer of fiber mass toward this end is promoted, and the incline upward is prevented.

The invention will now be explained in more detail by way of an exemplary embodiment.

In the accompanying drawing: Figure 1: shows a schematic longitudinal section through a sorting apparatus comprising a rotating drum screen 1; Fig. 2: shows a corresponding cross-section and Fig. 3: shows a partial longitudinal section related to the former.

The cylindrical drum screen 1 is mounted in a housing and is rotated by means of an actuator, with the axis of rotation 3 slightly inclined relative to the horizontal. This slight slope promotes transport towards the outlet 14.

As shown in Fig. 1, there is a disintegration zone 8 adjacent to the left end 4 in order to disperse the recycled paper. The consistency of the pulp slurry resulting from this decomposition is about 18%.

For further processing of the pulp 2, the disintegration zone 8, as shown in Fig. 1, is provided with an axially sorting zone 9 along which the drum screen 1 is perforated, whereby the fine fraction flows through the perforation and passes from the drum 1 to the collection container 13. The portion retained by this perforation is discharged as coarse fraction or reject through the outlet 14 at the right end 5 of the drum screen 1.

Above the screening zone 9, a spraying device is often provided which directs water to the perforation. This cleans the perforation and additionally causes the pulp slurry to further dilute within the sorting zone 9. In order to disintegrate the fibrous mass 2, mainly consisting of recycled paper, the drum screen 1 has on its inside lifting elements 6 in the form of hoists or similar structures. Such structures are known for their various forms and are adapted to the particular application. In addition, the drum screen 1 inside of the periphery is also attached to the rotation axis 3 in the form of inclined siirtorimojen the transfer elements 6.

In order to achieve an axial transfer power directed towards the opposite outlet opening 14 of the drum screen 1, the end of the transfer bar pointing in the transfer direction follows with respect to the other end in the direction of rotation 15.

Even if the drum screen 1 is divided into a plurality of partitions 10, which are open in the middle and generally perpendicular to the axis of rotation 3, the transfer elements 6 can pass the pulp 1 through the opening 11 of the partitions 10 without any problems.

As the contaminants accumulate in the drum rotation axis 3 of the screen 1 easy access to the area kehräytymiksi and finally the braid is as shown in Figures 2 and 3 of the screen drum 1 mounted on the inside of the periphery, in particular welded, more than one vortex ring elements 7 which extend radially from the drum screen in one. These vortex flow elements 7 extend clearly over the lifting and transfer elements 6 and extend to a range of average fill height, i.e. to the slurry surface of the drum screen 1. In this way, the vortex flow elements 7 can form a relatively large vortex in the center of the drum screen 1, which at least prevents spinning.

In order to enhance the interaction between the vortex flow elements 7, the vortex flow elements 7 should be at least slightly overlapping with respect to the periphery of the drum screen 1 in order to improve the interaction between the vortex flow elements 7.

As illustrated in Figures 2 and 3, the eddy flow elements 7 are formed as plates which extend substantially perpendicular to the axis of rotation 3 and taper towards the axis of rotation 3. In this embodiment, the forces acting on the vortex flow elements 7 during rotation of the fibrous mass 2 remain controllable. In addition, the rotating edge of the plate thus results not only in swirls but also in the breaking of spinning or even braiding.

For ease of attachment, the vortex flow elements 7 are always between two lifting and / or transfer elements 6 arranged in a row circumferentially. This in turn enables the vortex flow elements 7 to be secured to the inner side of the drum screen and to the lifting and transfer elements 6.

Claims (12)

SUGGESTIONS T A rotary drum screen (1) for treating fibrous pulp (2) having an axis of rotation (3) inclined up to 30 ° with respect to the horizontal, fed from the first end (4) with water mixed with pulp (2) thoroughly lifted within the drum sieve (1). - and / or transmission elements (6) and transported from the first end (4) to the second end (5), characterized in that the drum screen (1) inside which is mounted a vortex flow elements (7) having a height across the inside of at least 25% of the drum sieve the diameter Asta. 2. The claim 1 rotary drum screen according to (1), characterized in that the vortex flow elements (7) has a height across the inside of at least 30%, preferably at least 35% of the diameter of the drum screen. Rotary drum screen (1) according to one of the preceding claims, characterized in that the vortex flow elements (7) are formed as plates. A rotary drum screen (1) according to claim 3, characterized in that the plate-like eddy flow elements (7) extend circumferentially to at least one essential directional component. Rotary drum screen (1) according to protection claim 3 or 4, characterized in that the plate-like eddy flow elements (7) extend radially to at least one essential directional component. Rotary drum screen (1) according to one of the preceding claims, characterized in that the vortex flow elements (7) taper towards the axis of rotation (3). Rotary drum screen (1) according to one of the preceding claims, characterized in that the vortex flow elements (7) are arranged between two lifting and / or transfer elements (6) arranged in a row circumferentially. Rotary drum screen (1) according to one of the preceding claims, characterized in that the disintegration zone (8) following the first end (4) of the drum screen (1) is axially associated with a sorting zone (9) with a portion of the drum screen (1) flows through the hole and separates the coarse fraction from it. A rotary drum screen (1) according to the protection claim 8, characterized in that the vortex flow elements (7) are arranged in a disintegration (8) and sorting zone (9). Rotary drum screen (1) according to one of the preceding claims, characterized in that the transfer elements (6) are formed as displacement ribs attached to the inside of the drum screen and inclined with respect to the axis of rotation (2). A rotary drum screen (1) according to one of the preceding claims, characterized in that the transfer elements (6) are formed as coils fixed on the inner wall of the drum screen (1). Rotary drum screen (1) according to one of the preceding claims, characterized in that the lifting elements (6) are arranged inside the drum screen as lifting ribs (10) which have no axial transfer power.